Collaboration and License Agreements - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended			1 Months Ended							12 Months Ended		1 Months Ended					12 Months Ended			12 Months Ended		1 Months Ended	12 Months Ended	1 Months Ended			12 Months Ended		6 Months Ended	12 Months Ended
	May 31, 2013	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 30, 2012 Novartis AG ("Novartis")	Feb. 28, 2009 Novartis AG ("Novartis")	Apr. 30, 2012 Novartis AG ("Novartis") Absent Collaboration Revenue Acceleration	Aug. 31, 2009 Merck & Co., Inc. (“Merck”)	Jul. 31, 2009 Merck & Co., Inc. (“Merck”)	Nov. 30, 2012 Biogen Idec	Oct. 31, 2011 Biogen Idec	Dec. 31, 2013 Biogen Idec	Dec. 31, 2012 Biogen Idec	Oct. 31, 2011 Biogen Idec Phase 2 Clinical Trial	Oct. 31, 2011 Biogen Idec Phase 3 Clinical Trial	Oct. 31, 2011 Biogen Idec Milestone One	Oct. 31, 2011 Biogen Idec Milestone Two	Oct. 31, 2011 Biogen Idec Convertible Preferred Stock	Dec. 31, 2011 Biogen Idec Collaborative Arrangement	Dec. 31, 2011 Biogen Idec Under Previous Accounting Guidance for Multiple Element Arrangements	Dec. 31, 2013 Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer")	Dec. 31, 2013 Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") Collaborative Arrangement	Dec. 31, 2012 Bristol-Myers Squibb Company ("BMS") and Pfizer Inc. ("Pfizer") Collaborative Arrangement	Jan. 31, 2013 Lee’s Pharmaceutical (HK) Ltd (“Lee’s”)	Dec. 31, 2013 Lee’s Pharmaceutical (HK) Ltd (“Lee’s”) Collaborative Arrangement	Feb. 01, 2013 Bayer Pharma, AG (“Bayer”)	Feb. 01, 2013 Janssen Pharmaceuticals, Inc. (“Janssen”)	Feb. 01, 2013 Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen")	Dec. 31, 2013 Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") Collaborative Arrangement	Dec. 31, 2013 Aciex Therapeutics, Inc. (“Aciex”)	Jun. 30, 2013 Daiichi Sankyo, Inc ("Daiichi")	Dec. 31, 2013 Daiichi Sankyo, Inc ("Daiichi")	Dec. 31, 2013 Daiichi Sankyo, Inc ("Daiichi") Collaborative Arrangement	Dec. 31, 2013 PORTOLA PHARMACEUTICALS INC
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront and non-refundable fee														$ 75,000,000		$ 50,000,000			$ 36,000,000													$ 700,000		$ 2,500,000	$ 2,500,000	$ 5,000,000
License fee receivable upon occurrence of certain development and regulatory events														505,000,000			420,000,000	370,000,000	508,500,000			23,000,000	485,500,000
Clinical trial costs company must fund														18,000,000					1,000,000
Increase in collaborative revenue										1,169,000	(65,426,000)	(35,387,000)	65,100,000
Impact of scenario on net income															(65,100,000)													3,400,000
Net income (loss)		(25,062,000)	(18,550,000)	(21,598,000)	(18,142,000)	(13,781,000)	(11,488,000)	49,762,000	(13,127,000)	(83,352,000)	11,366,000	19,984,000			53,700,000
Net income (loss) per share													$ 0.00		$ (3.98)
Sale of stock, value																										9,000,000
Stock issued during the period	9,686,171																									636,042
Premium on sale of stock																										1,100,000
Estimated partial reimbursement of research and development services																			22,900,000
Non-contingent consideration being recognized as revenue over estimated period of performance																								36,000,000	22,900,000															3,000,000	581,000
Collaboration revenue recognized																											37,100,000			4,000,000	2,000,000		194,000				3,900,000				2,400,000
Reduction in research and development expense																				804,000	6,500,000						734,000
Performance period																			2 years
Notice period for agreement termination																		120 days														60 days
Deferred revenue																													6,000,000				506,000				1,100,000
Additional non-refundable fee																																		250,000	250,000	500,000
Development costs, percent																																						60.00%				40.00%
Research and development										79,286,000	49,717,000	46,089,000																										0
Collaborative arrangement upfront payment to be received																																							6,000,000
Upfront fee subject to refund																																							3,000,000
Contingent consideration to be recognized after resolution of contingency																																								3,000,000
Contingent consideration of collaboration arrangement																																									$ 3,000,000